Nonwoven fibrous structures have been around for many years and today there are a number of different nonwoven technologies in commercial use. To illustrate the breadth of nonwoven technologies, paper is probably one of the earliest developed nonwoven fibrous structures. Nonwoven technologies continue to be developed by those seeking new applications and competitive advantages. One broad market area that has proven to be highly desirable because of its large volume and economics is the protective apparel market. This market comprises protection from hazardous chemicals such as in chemical spill clean up, from liquids such as blood in the medical field and from dry particulates or other hazards such as painting or asbestos removal. This market is served by a number of competing technologies.
Focusing simply on the medical protective apparel market, E. I. du Pont de Nemours and Company (DuPont) makes Sontara.RTM. spunlaced fabrics which are used extensively for medical gowns and drapes and, for certain applications within the medical field, Tyvek.RTM. spunbonded olefin.
Sontara.RTM. spunlaced fabrics have long been used in the medical field because of their exceptional performance and comfort. Sontara.RTM. spunlaced fabrics for medical protective apparel uses are typically comprised staple length polyester fiber hydroentangled with woodpulp. The fabric is finished with a moisture repellent coating to render it strike through moisture resistant.
Tyvek.RTM. spunbonded olefin is particularly useful in medical packaging where it provides valuable advantages such as permitting sterilization in the package. It also is extremely low Tinting thereby minimizing contamination in the operating room.
Other technologies that compete in the medical field include composite or laminated products. The composite provides a balance of properties suitable for the end use. One competitive technology is generally called "SMS" in the industry for Spunbond/Meltblown/Spunbond. The basic SMS nonwoven material is described in U.S. Pat. No. 4,041,203 with further improvements described in U.S. Pat. Nos. 4,374,888 and 4,041,203. The spunbond outer layers are comprised of spunbond nonwoven which provides strength but is not able to attain the barrier properties of the meltblown inner layer. The technology for making meltblown fibers is swell suited to making fine low denier fibers which are able to have barrier and breathability but is not suited to obtaining suitable strength to withstand use as a garment.
U.S. Pat. Nos. 4,622,259 and 4,908,163 are directed to an improvement over SMS technology by making the meltblown fibers with improved tensile properties. By providing better meltblown fibers, one may avoid applying the scrim reinforcement and obtain a lighter weight fabric.
It is an object of the present invention to provide a further improved nonwoven structure which has a balance of properties which are better suited to barrier end uses.
It is further object of the present invention to provide a nonwoven structure that has more substantial barrier and breathability properties compared to currently known barrier materials.